I think you may be borderline on having enough light for plants. That Marineland Double Bright light barely gives you 20 micromols of PAR at 24 inches distance. A Finnex Ray2, 24 inch long light, hanging about 6 inches above the top of the tank would give you much better, but still low light. (Right at the top of the tank it might give a bit too much light for low light conditions.) I think that is the change I would make.